Lost Fuel efficiency

I have a 2001 Rodeo and recently I have noticed that it is getting about 3-4 mpg less than it used to. I have tried higher octane gas, fuel injector cleaner, and I have switched to a synthetic blend oil. My next step is to replace the spark plugs. (I haven't done this yet because it is not suggested to change them until 100,000 miles, and I only have 42,000.)

Is there anything else that might cause this?
Oh yeah, I checked my air filter and it's clean.

Welcome!

Our moderator Amigo-2K, has some answers here:

http://isuzufaq.ibctech.ca/#faq8

If you get a chance, scan that page for other issues that might relate to your Rodeo.

Good luck!

other than the poor mileage, is it running rough? Maybe a clogged fuel filter.

Marc

the main things to check clean is the EGR, EGR port Fuel Filter and a leakin intake manifold gasket, front out of alignment (these will all lead to lower MPG).

Also, sluddge build up and carbon build up will too (search here and the faq's for sea foam).

Plugs should be done at about 50k. 100k is a lot. Steel plug threads in an alumin block for 100k is a bad idea.

I reaplaced mine at about 50k. The still looked great, and I could of honestly just regapped them, lubed them up and stuck them back in

I read the information on the link that you provided thanks.

The truck runs smoothly, but as stated the mpg has gone down.
I saw something about the PCV valve. I did a quick look around the engine the other day, and I couldn't see the PCV valve. Where is it on the 4 cyl. engine for the 2001 Rodeo?

hold the boat.

the faq's are for 3.2L v6.

Around 15-20mpg is about right for a stock 1998+ 2.2L or 3.2L. I'd check your tire pressure and tire condition first, but if she's running fine and you have no check engine light, she's doing fine. MPG's can vary a bit based on ambient conditions and fuel used. Get that timing belt replaced on your 2.2L if you havent yet!! If it goes, so does your $$$$ valvetrain!
G/luck
Joel

That FAQ covers most stuff. If you want to improve on stock mileage, do the following.
1. Install manual hubs on the front. 1-2mpg
2. Switch to full synthetic in the diffs, transfer case and tranny. 1-2mpg
3. Use BG-44K fuel injector cleaner. It's 20 bux for a coke can size bottle, but unlike the 4 dollar fuel injector cleaners, it actually works. Napa can hook you up. You might not need it at 40k, but I know mine sure did at 80k.

1. Install manual hubs on the front. 1-2mpg
2. Switch to full synthetic in the diffs, transfer case and tranny. 1-2mpg.

The 1998+ 2.2L was only used on 2wd rodeos.
G/luck
Joel

Thanks for all of the good info.
I changed the spark plugs and the air filter this past weekend. So I'll see if this makes any difference.

Is the 2.2L in my 2001 the same engine that is in a 96 or 98 model?

..Is the 2.2L in my 2001 the same engine that is in a 96 or 98 model?

Your 2.2L was used only from 1998-2003. It's the same 2.2L used in the Daewoo Nubira (sp?). It was a General Motors 'global' design used by daewoo, isuzu and holden that never really took off. Check that timing belt and associated hardware ATLEAST every 30K miles!!
G/luck
Joel